The invention relates to a convoluted boot having a boot portion comprising annular folds, and collar portions adjoining the boot portion at both ends. A ventilation aperture is formed in the smaller one of the collar portions. The convoluted boot is provided for a universal joint which comprises an outer joint part and an inner joint part connected to a driveshaft. A larger collar portion is securable to the outer joint part and a smaller collar portion to the driveshaft.
Driveshafts whose universal joints are sealed by convoluted boots, in operation, are subject to pressure differentials between the joint and boot interiors on the one hand and the environment on the other hand. The pressure differentials may be due to differences between the operating temperature and the temperature of the environment, to the gassing behavior of the grease filling of the joint, to chemical reactions in the grease filling and to diffusion taking place through the convoluted boot wall. Such pressure differentials, especially a vacuum in the boot interior relative to the environment may cause the annular folds to collapse, especially during joint articulation. This results in inadmissible abrasion at the convoluted boot part. To avoid excessive pressure differentials it is known to provide convoluted boots of this general type with a ventilation aperture. A convoluted boot of such a type is known from DE 43 23 686 C2 wherein the connection between the ventilation aperture and the interior of the boot portion is permanently open. To avoid dirt or moisture from entering the interior of the convoluted boot in the assembled condition, the smaller collar portion, in its inside, is provided with a labyrinth channel for which there are proposed different shapes. Even with slight pressure differentials between the joint and boot interior and the environment, for example when driving through mud flat or water spray, a convoluted boot of this type fitted in a universal joint of a driveshaft of a motor vehicle allows the free entry of water or, at very high operating temperatures, loses greatly liquified grease.
It is therefore the object of the present invention to improve a convoluted boot of said type in such a way as to ensure a statistically small risk of moisture entering or grease emerging through the ventilation aperture.